The invention relates to a process for preparing organic monomeric or polymeric compounds carrying tert-butyloxycarbonyl (t-BOC) groups. Such compounds have diverse uses in light-sensitive coatings, such as are described, for example, in EP-A-0,102,450, EP-A-0,404,206 and EP-A-0,249,139 and DE-A 3,817,010.
Known processes for introducing the t-BOC group into monomers or polymers use compounds with heteroatoms, such as nitrogen or oxygen, to which an acidic proton is bound as starting materials. These compounds are dissolved in an inert solvent and then deprotonated by the addition of equimolar amounts of a strong base, such as potassium tert-butylate. The anion formed then is converted into the desired tert-butyloxycarbonyl group by the addition of di-tert-butyl dicarbonate which, if necessary, is dissolved in a solvent which is inert under the reaction conditions.
The disadvantages of this procedure result from the heterogeneous reaction system: since the anion formed has, as a rule, a low solubility, large quantities of solvent are required. It is also necessary to work with the exclusion of air and water, which complicates the preparation. By-products and waste products are formed, so an additional step is necessary to isolate and purify the desired products.
In EP-A-0,102,450, a preparation process is described which leads to the desired polymers with t-BOC groups by polymer-analogous reaction with the aid of phase transfer catalysis. In this process, again, the product formed must be isolated from the organic phase by precipitation.